In magnetic recording, and particularly in the case of portable magnetic recording devices such as a cartridge containing magnetic recording tape, it is important to provide measures to prevent inadvertent recording on the magnetic medium. This function, commmonly known as "file protect", is necessary to avoid accidental erasure of information already recorded on the medium and not intended to be replaced by recording over it. When enabled, the file protect function effectively disables the recording or writing circuitry of the device with which the medium is being used so as to prevent operation of the writing circuitry so long as the file protect feature is in operation.